Project Summary Acute myeloid leukemia (AML) is one of the most challenging malignancies with the 5-year survival for younger and medically fit patients hovering around the 30% mark for over 3 decades. About 30% of AML patients harbor activating mutations in FLT3 kinase that are associated with very poor prognosis. The non-specific tyrosine kinase inhibitor (TKI) Midostaurin was approved in 2017 for combination treatment with standard chemotherapy. However, remission achieved with this treatment, if any, is short-lived. FLT3-AML patients that relapse or are refractory to this treatment are treated with newly developed, more specific, FLT3 inhibitors Quizartinib and Crenolanib that are in clinical development or Gilteritinib that was recently approved. However, this treatment also eventually fails due to emergence of secondary FLT3 mutations within the tyrosine kinase domain and/or upregulation of compensatory resistance pathways. For these patients the time to death is around 3 months with no 3rd line treatment option available. KinaRx has developed a novel class of orally bioavailable 5-substituted aminonapthyridine TKIs that are active against secondary mutated FLT3 resistant to the 1st and 2nd generation FLT3 inhibitors. Extensive in vitro and in vivo data, including protection in orthotopic mouse models of drug resistant FLT3-AML presented in this proposal, establish our lead compound KRX-101 as the best-in-class FLT3 inhibitor and a strong candidate as 3rd line treatment option for FLT3 mutated relapsed or refractory patients that do not respond to gilteritinib, crenolanib or quizartinib. In this multiple PI, Direct to Phase II SBIR, we propose to advance KRX-101 through completion of IND-enabling studies. In Aim 1 we will technology transfer the synthesis procedure and analytical methods to CMO for process scale up, analytical development, and production of a 100 g demonstration lot. In Aim 2, we will complete efficacy data package including activity toward primary AML cells and efficacy in patient-derived xenograft models and conduct preliminary safety studies. Aim 3 will focus on developing a regulatory strategy and holding a Pre-IND meeting with FDA. A GLP toxicology lot (5 kg) will be produced in Aim 4 and used to conduct a full battery of IND-enabling GLP safety-pharmacology studies in Aim 5. The project brings together a strong team of investigators with decades of experience in drug discovery and development: Dr. Holtsberg, VP of Operations at KinaRx with 25 years of experience in pharma and biotech, Dr. Sintim, Professor of Chemistry at Purdue University an expert in anti-cancer drug discovery and the inventor of KRX compound series, Dr. Emadi, Professor of Hematology and Oncology at University of Maryland (UMB), a highly experienced clinician, former regulatory officer at FDA, and a recognized expert in hematological malignancies with a focus on clinical research and management of AML, Dr. Lapidus, Associate Professor at UMB, an expert in animal models of hematological malignancies, seasoned ex-FDA and ex-Pharma subject matter experts in development of oncology drugs from RRD International, and two of the most experienced contract manufacturing (CMO) and contract research (CRO) organizations Olon-Ricerca and Frontage.